In a statement Monday, the Afghan military said three other US troops were wounded in the explosion and were receiving treatment.
The Taliban has claimed responsibility for the attack and described it as a suicide car bombing, rejecting the US forces’ account of the incident.
The group said an attacker detonated his explosives-laden vehicle near the base in Parwan province.
Iranian media reports have described those killed in the attack as “American terrorists.”
Located in Bagram district in northern Parwan province, the base serves as the main US air facility in the country.
The fatalities bring to seven the number of US soldiers killed in Afghanistan so far this year.
Last year, 13 US service members were killed in the country.
Six soldiers killed as Taliban attack US-Afghan baseThe Taliban stormed an Afghan army base in Helmand as talks with the US are temporarily halted in Doha.
The Taliban have continued to carry out daily attacks on Afghan security forces despite holding several rounds of peace talks with the United States in recent months.
The Taliban’s five-year rule over at least three quarters of Afghanistan came to an end following the US-led invasion of the country in 2001. But 18 years on, Washington is still entangled in the war and is now seeking a truce with the militants.